My 99 ext cab 5.4 auto 3.55LS has just hit 101,000 miles. I'm a do-it-yourselfer at heart. Just changed the diff lube with royal purple 75-140w and very satisfied. Only thing is, the front seal to the diff just behind the U joint has and is leaking. It's not much, but a leak is a leak. What does it take to replace this or is it a job for the dealer or a mechanic else where?

 

I'm guessing you are talking about the pinion seal. ANd I hope you didn't use 75w140 in the front diff. It should take 75w90. To replace the pinion seal, you have to remove the front driveshaft and remove the flange from the pinion. The seal can be pryed out. Tap the new seal in and put the flange back in. You will need either a big breaker bar or an inpact to tighten the flange nut and be sure you don't over tighten it. Hope this helps.

 

No not the front diff, I wish. My truck is a 4x2 only. Yeah,,,,talking about the pinion seal.

 

it always is a good idea to mark the pinion, flange, and nut. then just make sure they all line up when done. if you do it on the ground apply the park brake to hold the pinion so it doesn't turn when loosening up the nut. you can count the number of turns when backing off the nut, then make sure the lines match up on the pinion and nut when tightening to ensure it doesn't get over tight. also make sure the garter spring on the old seal doesnt't get left on the pinion, it can get pinched between the flange and oil slinger and cause a vibration in the drive line. good luck